Principles of external fixators

Indications
External fixation has a vital role in both provisional and definitive fracture fixation.
In provisional stabilization, the surgeon must consider the impact of the fixator on the patient’s care (wound and hygiene) and definitive management.

1- Fractures With Soft-tissue Damage
Closed ,open fractures and after fasciotomy

2- Polytrauma—Damage Control Surgery
Provisional application of external fixator as fast as possible to stablise the patient and save life and limb.
3- Skeletal Infection
4- Corrective Surgery And Bone Transport
5- Arthrodiastasis and Joint Fusion

6- Indirect Reduction By Ex fix or Distractor

Frame Configuration
A- Unilateral.
B- Bilateral.
C- Multiplanar(quadrilateral)
D- Multiplanar (deltaconfiguration).
E,F- Ring fixator

Types
1- Single Tube 2- Modular

3- Ring 4- Hybird

5- Monolateral Dynamic Lrs and ball joint spaning orthofix

Basic Implants
1- Schanz Screws
Size never use more than one third of bone diameter
Pin bending strength is increased to the fourth power of the increase in the pin’s radius
5-6 mm for femur and tibia
4-5 mm for humerus
4 mm for forearm
2-3 in hand and foot
Avoid thermal necrosis
Preloading ,irrigation and t handle insertion
Avoid skin damage
Use asleeve
Know the safe zones well.
2- Clamps
3- Rods

Safe Zones
Humerus
Pins (5 mm) are placed anterolaterally in the proximal humerus, taking care to avoid damage to the axillary and radial nerves, and posterolaterally (4 to 5 mm) in the distal humerus, avoiding the olecranon fossa .
Femur
Femoral shaft fractures are stabilized using pins (5 mm) placed anterolaterally or directly lateral .

Wrist
30°-40° in relation to the sagittal plane to avoid transfixing the extensor tendon/hood
The proximal two pins should be inserted proximal to the muscle bellies of abductor pollicis longus (APL) and extensor pollicis brevis (EPB), and should not penetrate them.

Tibia
Proximal tibial head
2CM distal to tibial plateau and avoid patellar tendon transfixion .
Distal of the tibial tuberosity
Tibial crest and the medial face of the tibia

Factors Adding To Stability Of External FixationI
1- The stiffness of the frame increases with the thickness of a screw.
2- The thread design will define the holding strength in the bone.
3- It is better to insert a pin as close as possible to the fracture site.
4- Through larger distances between the pins in a fragment, the holding strength increases.
5- Also, a second rod will additionally increase the stiffness.